U^^B^Tc/zMT-M^
A PREUMINARY SURVEY
OF THE BATS OF THE
DEERLODGE NATIONAL FOREST
MONTANA
1991
Rnal Report
September 1993
Thomas W. Butts
Montaia Natural Heritage Program
1515 East Sixth Avenue
Helena, Montana 59620
forihe
Deerlodge National Forest
U.S.DA Forest Service
Butte,Montana
© Hntan totural Hadtage Progn
This dooment should be cited as follcws:
Butts Thonas W. 1993. A prelUninary suivey of the bats of the Deerlo^
National Forest. Montana. Montana Natural Heritage Prograni. Helena, m. 35 pp.
599.4
N11PSDNF91
1993
1
_&j.tt^ILL
Montana State Library
3 0864 1004 3980 4
ox aanssi
TABLE OF CONTENTS
Page
INTRODUCTION 1
ACKNOWLEDGEMENTS 3
METHODS 4
Equipment 4
Bat identification 5
Site selection 6
Caves and adits 7
Habitat use surveys 8
RESULTS 10
Habitat use surveys 10
Bat species captured 15
Cave and adit surveys 17
DISCUSSION 22
Survey methods 22
Species oocurrenoe 23
Relative density 25
Habitat use 26
Cave and adit surveys 30
SUNf^ARY 30
LITERATURE CITED 32
APPENDIX I 34
LIST OF TABLES
Page
Table 1. Habitat components and survey results by site.
Deer lodge National Forest, 1991 12
Table 2. hfumber and percentage of sites with high and
moderate bat activity for a given habitat
corrtponent 14
Table 3. Percentage of sites with high and moderate bat
activity featuring a given habitat conponent 15
Table 4. Bats captured on the Deer lodge National Forest,
1991 16
LIST OF FIGURES
Page
Figure 1. Map of Deerlodge National Forest and survey
sites, 1991 11
INTRODUCTION
There are more species of bats worldwide than any other group of
mammals except rodents, totalling some 950 species with nearly
worldwide distribution (Hill and Smith 1984). Most are considered
beneficial to man, and play key ecological roles as plant pollinators
and voracious insect eaters, yet as a group few mammals have been
more misunderstood. Today, many species of bats are potentially
threatened with extinction, and most bat populations have been
reduced due to direct attempts at extermination, indirect loss
through pesticide poisoning and roost distiorbanoe, and loss through
degradation of food sources and habitat loss or alteration (Fenton
1992).
The National Forest Management Act of 1976 and United States Forest
Service (USFS) policy require that Forest Service land be managed to
maintain viable populations of all existing native and desirable non-
native plants, fish, and wildlife (FSM 2601.2). A viable population
has the size and distribution of reproductive individuals to ensure
continued existence of the species throughout its existing range (FSM
2605 ) . Species recognized by the Forest Service as needing special
management in order to meet this objective are those designated under
the Endangered Species Act as threatened or endangered, those
candidate species londer consideration for such designation, and those
classified as Sensitive Species. Sensitive Species are plant and
animal species identified by the Regional Forester for which
population viability is a concern as evidenced by a significant
downward trend in pc^xilation numbers or habitat capability that would
reduce a species' existing distribution (FSM 2670.5).
Additionally, the Endangered Species Act Section 7 (a)(2) mandates
the assurance by any federal agency that any of its actions "is not
likely to jeopardize the continued existence of any endangered or
threatened species or result in the destruction or adverse
modification of (its) habitat" (Finch 1992).
There are presently 14 species of bats in Montana (Thortpson 1982).
Three of these, the Townsend's big-eared bat (Plecotus tounsendli) ,
the Spotted bat (Euderma maculatun ) , and the Pallid bat (Antrozous
pallidus) are listed as sensitive species by USFS Region 1 (Mumma
1991). In addition to these three species, the Fringed myotis (Myotis
thysanodes) and the ^k^rthem long-legged myotis (ttyotis
septentrionalis) are also listed as species of special concern by the
Montana Natural Heritage Program (Center 1993). Several other
species have localized distribution in Montana. Relatively little
work has been done in the state to inventory species' distributicxis,
densities, and populaticn trends to date.
As the U.S. Forest Service has a responsibility to manage for species
viability on Forest lands, as required by the previously mentioned
legislation and rules, and as relatively little is known oonoeming
bats in Montana, and several Mcntana species are listed as sensitive
by the USFS and by the Montana Natural Heritage Program, the
biologist for the Deerlodge National Forest in southwestern Montana
cxntacted tt^ Montana Natural Heritage Program director to discuss
the possibility of developing baseline data on the occurrence,
distribution, relative density, and habitat use of bats on the
Forest. The results of the first year of study are presented here.
ACKNOWLEDGEMENTS
Field work for this study was performed by Tan Butts with the
assistance of Wendy Wilson and Jeremy Butts. Dave Center of the
Montana Natural Heritage Program provided direction, suggestions,
editing of reports, field assistance, equipment, and bat
identification. Jina Mariani, Deerlodge National Forest, Butte,
provided the impetus for the study, funding, a vehicle, and editorial
ccrments on the final report.
METHODS
Equipment
Mist nets: Braided nylon mist nets, in 18, 30, and 36 foot
lengths, (50 demier/2 ply; 1 1/2 inch mesh) were used to capture
bats (Kunz and Kurta 1988). Mist nets were strung on sectional
aluminum poles made from electrical conduit, cut to 5 foot lengths,
each with a connector at one end, so a net pole could be fashioned to
any desired height. Poles used for this study were two or three
lengths high (10 to 15 feet). Poles were held in place with ropes
tied to trees, rocks, or branches. Mist nets were deployed across
forest trails, across the narrower stretches of slow moving streams
and smaller pools, and adjacent to the shoreline of lakes and larger
ponds (Kunz and Kurta 1988).
Harp Trap: A modified collapsible harp trap (Kunz and Kurta
1988, Tuttle 1974) was constructed using 3 inch PVC pipe for the
frame and 10 pound monofilament fishing line strung between the
vertical members of the trap. The double- frame trap was used at the
mouths of caves and adits (Kunz and Kurta 1988).
Bat detectors: Tunable Broadband ultra-sonic bat detectors were
used to detect night-time bat activity. If a single detector was
being used it was tuned to 40 kHz vrf>en walking a transect. When a
bat was detected, the dial of the detector could be manipulated to
find the high and low range of the detected bat (if there was time.
which there generally was not). With experience, the activity of the
bat (cruising, searxdiing, or feeding) and the genus of the bat could
be determined by the sound, duration, and intensity of the detected
bat echolocations (Fenton 1988, Fenton and Bell 1981). Detections
were recorded on field forms by time, frequency monitored, and
species (if known or suspected) (See Appendix I for example of field
form used ) .
Tenperature in degrees fahrenheit was recorded in most adits and cave
using a Taylor Pocket thermaneter . Relative humidity was recorded at
these sites using a Princo Pocket sling psychrometer .
Bat identification
Once captured in a mist net or harp trap, bats were carefully
removed. Species of the bat, sex, age (juvenile or adult),
reproductive condition (females: lactating or non-lactating; males:
scrotal or non- scrotal ) , and select measurements (forearm length,
tibia length) and other identifying characteristics and measurements
such as ear length, pelage ooloraticn, etc., were recorded on field
forms. Methods of determining sex, age, and reproductive condition
are frotn Anthony (1988) and Racey (1988). Weight was recorded using
a Pesola spring scale ( 50g X .5g) and measurements were taken using a
dial caliper and recorded to the .5 millimeter. Bats were
identified using one of several dichotomous keys. The most useful
were:
Bats of America Barbour and Davis 1959
The Mammals of Montana Hoffman and Pattie 1968
Handbook of Canadian Mammals van Zyll de Jong 1985
Most bats were released after data were recorded, though if there was
a question of identification, or if the bat was considered unusual
for the locality or habitat, the bat was collected to be verified
later by a ooitpetent authority.
Site Selection
The following criteria were used in selecting sites to survey bat
distribution and habitat use on the Deer lodge Naticxial Forest:
1) the location and survey of caves and adits on the Forest
was a top priority;
2) representative habitats on the Forest were to be
surveyed;
3) suiveys were to be made throughout the Forest, and;
4) surveys were to be conpleted within a timeframe dictated
by bat behavior: at some time, typically in September,
bats would either hibernate of migrate out of the study
area.
The Forest was divided into three broadly defined zcaies; the
Phillipsburg and Anaconda area, the Boulder and Basin area, and the
Butrte area. Though habitats throughout the Forest were to be
sampled, the highest priority was assigned to the
Phillipsburg/Anaoonda zone due to the higher number of caves and
adits occurring within it, and the greater variety of habitats.
Caves and adits were located by consultation with Forest Service
personnel, knowledgeable "cavers," "locals," and existing literature,
particularly Campbell ' s ( 1978 ) Caves of Montana.
Other survey sites were chosen using the afore-mentioned criteria.
Once a general area was selected, the specific site was chosen that
appeared to have potential roosting sites nearby, such as older
trees, fractured rock, old buildings, or known caves or adits. If
water was nearby, specific sites to set up mist nets were generally
selected that crossed the slowest moving stretches of streams or
pools.
Caves and Adits
When a cave or adit was located, it was searched for evidence of bat
use (bats, droppings, characteristic odor) and the location, extent,
potential for bat use, temperature, humidity, and other pertinent
data were described on field forms.
Caves or adits that were potentially used by bats were surveyed by
setting up one or more mist nets at or near the opening, or a harp
trap within the entrance, shortly before dark, and monitoring the
nets throughout the night. Mist nets were collapsed shortly before
dawn. An observer also used one or more bat detectors at the
entrance, beginning at dusk and staying at least an hour, and then
until there was no bat activity for more than 30 minutes.
Habitat Use Surveys
Once a site was selected, from two to five mist nets were set up in
the evening across trails, next to laJceshores, and across streams or
ponds (Kunz and Kurta 1988). Nets were not raised into final
position until about one-half hour after sunset to avoid catching
birds. Depending on the site, the height of the bottom of the net
above ground or water varied from less than a foot to 6 feet. Nets
were checked at least every hour until after midnight, then again
between one hour, and one-half hour before sunrise. Nets were taken
down one-half hour before sunrise to avoid catching birds.
One or two walking transects were conducted at each site, depending
upon available personnel. Beginning approximately one-half hour
after sunset, and lasting for one hour, a transect was walked through
habitat representative of the area, using one of the bat detectors.
All bats heard were recorded as "cruising, searching, or feeding, "
depending on activity, by species if identifiable, and by time
period.
A few transects were run during the middle of the night (between 1 AM
and 4 AM), or before sunrise, but so few bats were recorded that this
practice was abandoned.
Habitats sanpled for bat activity were broken into several habitat
conponents for analysis. The ccitponents were:
COMPONENT CODE
Etense lodgepole pine forest Lpp
Mixed hardwoods Mh
Mature Douglas fir DF
Sub-apine fir/limber pine SF
Clearcuts nearby CC
Lake nearby La
Ftock outcrops nearby Fto
Cave/Adit nearby Ca
Riparian (willow, alder, aspen) Ri
Beaver ponds nearby Be
Sites were assigned codes determined by habitat oonponents at or near
that site, and bat occurrence and relative density (meastired by bat
passes recorded per hour of walking transect) using various habitats
was determined.
Mixed hardwoods were primarily cottonwoods and/or aspen stands.
Mature Douglas fir stands consisted of trees generally 18 inches
diameter at breast height (DBH). "Nearby" habitat components were
within 1/4 mile (440 m) of the survey sites.
RESULTS
Habitat Use Surveys
Twenty-three sites (x\ the Deerlodge National Forest were visited cxie
or more times (Figure 1), and at least one walking transect was run
at each of these sites. At some sites two one-hour transects were
run in the evening, at two sites transects were run after midnight,
and at two sites transects were run 1 hour before dawn. One site was
visited 3 times, and two were visited twice. Mist nets were set up
at 19 of these 23 sites (Table 1), and the harp trap was enployed at
one site (twice) on the Deerlodge National Forest.
No bats were heard during any 1 hour transect run after midnight. In
30 hours of transect run before midnight, 33% recorded no bats, 53%
recorxied between one and 9 bats, and 10% recorded more than 21 bats
in one hour ( Table 1 ) .
Habitat components of sites with high bat activity (more than 10 bat
passes per ho-or), moderate bat activity ( between 5 and 9 bat passes
per hour), and low bat activity (less than 5 bat passes per hour)
were analyzed to isolate significant features of habitat used by bats
on the Forest. If more than one transect was run at a site, the
transect with the most passes per hour was used for site
classification. The records of bat passes per hour for Queen's Gulch
and Muskrat Creek were lost. As 10 bats were captured at Queen's
Gulch in one evening, the most at one site on the Deerlodge National
10
1)WEST FORK CAVE
2) THE CRATER
3) BOULDER CREEK
4) DONEY LAKE
5) ABOVE ROCK CREEK LAKE
6) ECHO LAKE
7) SWAMP GULCH
8) HEMDERSON CREEK
9) FRED BURR LAKE
10) HAIRY LIP CAVE
11) CRYSTAL CREEK C.G.
12) SAND BASIN
13) ROCK CREEK
14) MAXVILLE CAVE
15) BISON CREEK
16) BOULDER RIVER
17) BEAVER CREEK
18) NORTH OF BASIN
19) BLUEBELL MINE
20) ADIT #2 BERNICE
21) MUSKRAT CREEK
22) QUEEN'S GULCH
23) LITTLE BOULDER RIVER
Figure 1: Map of Deerlodge National Forest and Survey Sites, 1991.
11
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Little brown bat.
Hoary bat, Yuna
myotls. Long-
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12
Forest during 1991 surveys, high activity was presumed. Muskrat
Creek was rxDt used in the following habitat analysis.
Five of 23 sites siorveyed had high activity. Two of these sites.
Queen's Gulch and above Rock Creek Lake, were along small streams in
mature Douglas Fir forest with nearby rock outcrops (Table 1). The
other three were also near streams, had somewhat nearby rock
outcrops, nearby beaver ponds, and nearby mature hardwoods (Bison
Creek, Ftock Creek, and Crystal Creek Campground).
Sites with moderate bat activity included the Crater, Doney Lake,
Hairy Lip Cave, Echo Lake, Henderson Creek, and Sand Basin (Table 1).
Two of these sites had a cave nearby (both with clearcuts nearby as
well ) , two had a lake nearby ( one with a clearcut nearby ) , and two
were along small streams with riparian vegetation. One of these,
Henderson Creek, had all of the ccnponents of the sites with high bat
activity (mature hardwoods, beaver ponds, Douglas fir), and the other
had rock outcrops and clearcuts nearby.
The number of sites svirveyed that contained a given habitat
oonponent, and the number and percentage of these sites that had high
or moderate bat activity is shown in Table 2. For instance, 11 sites
had rock outcrops nearby. Of these 11 sites, five had high bat
activity (45% of the sites with rock outcrops), and 2 had moderate
activity (18% of the sites that had this ccnponent). By deducticxi.
13
Hdfcit-at ccx:^.rxvr\t
» of sites
Burveyod
» with Kit*-!
artivity
». with hi.^i
activity
» with
moderate
ac-tlvity
% wiu.
moderate
activity
Ftock out(jiups
11
1
45
2
18
Caves /adits
7
0
0
2
29
Riparian
18
5
28
3
17
Beaver ponds
5
3
60
1
20
Douglas fir
12
4
33
2
17
Cleancuts
4
0
0
4
100
Lodgepole pine
11
2
18
4
36
Lakes/ponds
3
0
0
2
67
Mature hardwoods
8
3
38
1
13
Riparian/Etoug . fir
and/or Mat. hrdwd.
15
5
33
2
13
Riparian/Rock out.
11
5
45
2
18
Table 2: Number and percentage of sites with high and moderate
bat activity for a given habitat conponent.
37% of the sites with rock outcrops had low bat activity. Habitat
features in vrfiich one-third or more of the sites with those features
had high bat activity were: beaver ponds (60%), rock outcrops (45%),
mature hardwoods ( 38% ) , and Douglas fir stands ( 33% ) . No high
activity sites were ever found near caves or adits, or near lakes.
Moderate bat activity was associated with the following components at
least one- third of the time that the component was available:
clearcuts (100%), lakes (67%), and lodgepole pine stands (36%) (Table
2).
Table 3 shows the percentage of high and moderate bat activity sites
14
Relative
Bat activity
High
100
100
60
80
40
66
Medium
33
33
50
17
33
66
66
33
17
Low
36
45
82
18
55
0
45
36
Table 3. Percentage of sites with high, moderate, and low bat
activity featuring a given habitat conponent (i.e 100%
of sites with high bat activity were near rock outcrops ) ,
containing a given habitat conponent. For instance, 100% of the
sites with high bat activity had rock outcrops nearby, and 100% were
in riparian areas. No high activity sites were near caves or adits,
but 33% of the moderate sites were. NkD high activity sites were near
lodgepole pine stands, or near lakes, but one- third of the moderate
activity sites were near lakes and two-thirds were near clear-cuts
(Table 3).
Bat species captured
Bats were captured at only five of the 19 sites that mist nets were
15
used on the Deer lodge Naticxial Forest. One bat was caught in the
harp trap at The Crater, cne bat in a mist net over a c:±iannel near
the main fork of Rock Creek, and 9 bats in mist nets upstream from
Rock Creek Lake west of Deer Lodge. One bat was captured in a mist
net on Muskrat Creek east of Boulder, and 10 bats were captured in
nets placed in Queen's Gulch in the Elkhoms. Location, species,
sex, and weight of bats captured on the Deer lodge Naticrjal Forest in
1991 is listed in Table 4.
There were six species of bats representing four genera recorded on
the Deer lodge National Forest during surveys in 1991. These were the
Little brown bat (Myotis lucifugus), the Lcaig-eared myotis {Myotis
evotls), the Yuma bat (Myotis yumanensis), the Big brown bat
(Eptesicus fuscus), the Hoary bat (Lasiurxzs cinereus), and the
Silver-haired bat ( Lasicoaycterus noctivagans) (Table 4),
Location
Species
Sex
Wt
Wingspan
Rock Creek
Silver-haired bat
M
11.0
303
The Crater
Yuma myotis
M
8.0
250
Rock Creek Lake
Yuma myotis*
"
Long-eared myotis*
"
Hoary bat*
••
Little brown bat*
Queen's Gulch"
Big brown bat
M
16.5
344
••
Long-eared myotis
M
5.0
245
Muskrat Creek**
Long-eared myotis
• Reoorda with D.L. Center. htiiUi7.n N-iniril Heritage Progran. Hels^.
*• C^txirad by Uendy UilBon and Br'Ky ^^il:m!^n. RBoorda vx«vall«ble.
Table 4. Bats captured on the Deer lodge National Forest, 1991,
16
Cave and Adit Surveys
A number of caves and mine adits were located and surveyed for
evidence of bat use on the Deer lodge National Forest. Caves that
were located and surveyed were:
Vfest Fork Cave SW 1/4 NW 1/4 Sec 36 T6N R6W
Located on the West Fork of Rock Creek just north of State
Highway 38 on state land about 1 1/2 miles west of the Rock
Creek forks, this is a large shelter cave, about 10 feet high
and 25 feet wide at the mouth, and 20 feet deep, with a steeply
sloping back wall. There is a chamber to the right of the
entrance that ends in about 15 feet. Some cracks in the walls
and ceilings extend out of sight and could be used by bats for
roosting, ^k^ evidence of bat use was found. The bat detector
was enployed for about an hour after dusk, at the mouth of the
cave, and no bats were detected leaving the cave.
Maxville Cave NE 1/4 Sec 16 T8N R13W
Located in a limestone outcrop about 1/2 mile SE of the
Boulder Creek road, and clearly visible above the trees, this
cave is reached by a steep trail through Douglas fir
forest. The opening is about 15 feet high and 3 feet wide. It
opens into a room 15 feet deep with an extension that dead-ends
within several feet and could be a bear den. ^to evidence of
bat use was found. On September 8 two mist nets were set up
near the entrance to this cave, and the bat detector was used
17
for 1 1/2 hours after dusk. No bats were heard or captured.
A few other small caves can be seen in limestone outcrops
southeast of this cave within 1/2 mile, but these were not
explored.
Wagner's Cave SW 1/4 Sec 23 T8N R13W
This cave is located in a limestone outcrop 3 . 6 miles southeast
of Maxville and west of Boulder Creek, The entrance is barely
visible from the road, just above the trees. It is necessary
to cross beaver ponds, wade Boulder Creek, and climb a steep
trail through Douglas fir forest, then ascend 25 feet of rock
to reach the mouth of the cave. A chamber at the mouth of the
cave quickly narrows to a 100 foot long horizontal passageway
about 4 feet high and 5 feet wide that leads to the first room.
Frxan this point there is a series of chambers and passageways
that extend perhaps 400 feet further.
Tenperature = 50 F
Humidity = 85%
This cavG was visited in July and in September. No evidence of
bats was found. Because of the steep and difficult terrain to
be negotiated, no atterrpt was made to haul the harp trap or bat
detector to the cave, though it may be worthv*vile.
Princeton caves Sec 30 T8N R12W
Three caves are visible high on a cliff side southeast of
18
Princeton and east of Boulder Creek. Spelunkers that have
visited them found no evidence of bat use (Hansen and Madsen,
pers. ocmm. ) .
The Crater NW 1/4 Sec 10 T8N RllW
Pikes Peak Creek siphcans into a hole in a limestone vrall and
completely disappears. Across from this siphon is an overhang
with a cave entrance about 4 by 4 feet that opens into a
chamber about 15 feet deep, 25 feet wide, and 30 feet high.
There are cracks in the ceiling that could harbor bats, though
no evidence of bat use was found.
Temperature = 50 F
Humidity = 74%
This cave was visited in July and in September. In July, the
harp trap was set up at the entrance to the cave, and a mist
net was placed across the pond nearby. A bat detector was used
near the entrance for two hours after dusk. No bats were
captured. Five bats were observed flying through upper tree
canopy at dusk, and 5 were heard in one hour on the detector,
but ncMve came out of the cave.
On September 9 the harp trap was set up in the entrance to the
cave, and two mist nets were placed acxoss the small the
opening in front of the cave. The bat detector was used for 1
1/2 hours after dusk, near the mouth of the cave. One cruising
Myotls was observed at dusk, and one was heard within an hour
19
after dusk, but neither came fron the cave. One bat,
tentatively icJentified as a Myotis yiiaanensis male, was
captured in the harp trap as it exited the cave.
Hairy Lip Cave
The entrance to this cave is located in an old clear cut 3.8
miles west of the Storm Lake junction south of the Peterson
Meadows rxDad. Because the cave drops into a deep pit about 15
feet past the mouth of the cave, temperature and humidity were
not taken. At dusk en August 5, one Myotis was seen leaving
the cave mouth, and heading north, and another was heard with
the bat detector in a 15 minute period. Mist nets were set up
around the entrance but no bats were captured.
Spelunkers that have been down in the cave reported seeing no
bats (G. Hanson and M, Madsen, pers. oom.).
This cave was again visited on September 25. The weather
was clear and cold. The bat detector was used at the
entrance for two hours. No bats were heard.
Garrity Cave
This cave is located on a high ridge northwest of Anaconda. An
all-wheel drive vehicle is apparently necessary to reach this
cave, thus it was not visited, Spelunkers that have been in
20
this cave did not notice bat evidence but it deserves to be
investigated (G. Hanson and M. Madsen pers. oomm).
Other caves
Several caves are located on a high ridge in the Pintlars south
of East Fork Reservoir. These caves could not be located
though they were searched for with the assistance of the
Missoula Grotto spelunkers.
Mine Adits
Several mine adits were visited between Basin and Bemice. An
adit north of the highway came to a dead end about 40 feet into
the mountain. No bat evidence was observed. Temperature 54
degrees, humidity 59%.
An adit about 1 mile east of Bemice on the south side of the
highway forked about 100 feet in. No bat sign was observed.
The bat detector was used for 2 hours after dusk at the
entrance. No bats were heard. Tenperature 46 degrees,
humidity 80% .
Two adits at the Bluebell Mine were searched for bat evidence.
None was found. Two mist nets were set up near the entrance
to one entrance, and the bat detector was used for 1 1/2 hours
after dusk. No bats were captured or heard. Temperature 47
degrees, humidity 66%.
21
DISCUSSI(>I
Survey methods
A study designed to determirie absolute and quantitative abundance of
a species is a census. Several methods, such as mark-recapture and
visual counts (Thanas and LaVal 1988), have been used by researchers
to estimate absolute bat numbers, but these have generally been in
enclosed areas such as caves, or at specific roosting or maternity
sites. Determining quantitative measures of bat densities in a given
habitat or foraging within a given area is not ocffisidered possible
with current technology (Findley 1993, Thomas and West 1989).
A survey is designed to provide relative and qualitative information,
in short to "respcxi(d) to such questions as. Does habitat A have more
bats of a given species than habitat B does? or Is species X more
abundant before or after modification of habitat Y?" (Thomas and West
1989). Findley (1993) concluded that the best that can be done by a
comnunity ecolcgist studying bats is to assess the relative abundance
of different species and to corpare regions and habitats with respect
to the numbers of bats obtained for given amounts of effort applied.
Summer roost counts, visvial counts of foraging bats, ultrasonic
detectors, vampire bites, and mist-netting and trapping were methods
listed by Thomas and LaVal (1988) to estimate bat abundance in
habitats or other geographic areas. The use of ultrasonic detectors
22
and mist-netting were selected as methods for ttiis study as no summer
roost sites were known in the study area prior tho the study, there
are no vampire bats, and visioal counts are limited to a short time
after dusk, prior to the time many species in Mcntana emerge from day
roosts.
Species occurrence
One of the objectives of this study was to document the occuirerce of
bat species on the Deer lodge National Forest. There are 14 species
of bats in Montana (Thompson 1982). Several of these are not
expected to be on or near the Forest due to limited distribution in
the state, such as the Spotted bat {Euderma maculatun) and the Pallid
bat {Rntrozous pallidus) , both apparently restricted in Montana to
the vicinity of the Pryor Mountains south of Billings (Vtorthington
and Ross 1990). Most of the species known to inhabit the state,
however, could potentially be found on the Forest. Documentation of
both general species diversity, as well as the occurrence of species
suspected of being relatively uncommon, such as Townsend's big-eared
bat (Plecotus townsendli) , is necessary for Forest planning and
management, considering the mandates of federal legislation to manage
for species diversity, and to maintain viable populations.
Though an experienced observer can identify many bat species visually
by size, shape, and flight characteristics, when light conditions
allow, documentaticn was not considered positive for this study
23
unless specimens were captured.
Capturing bats with mist nets incorporates several biases. In this
study, nets were never more than 15 feet above the ground, and
therefore selected against the capture of high flying foragers.
Other bats, such as the Townsend's big-eared bat are slow,
maneuverable flyers that can usually detect and avoid a mist net or a
harp trap, and thus are difficult to document by capture with these
techniques. All insectivorous bats are probably capable of detecting
and avoiding mist nets using echo- location. Few bats are thus
captxired while foraging. Most bats captured are probably "oonmuting"
along habitually used pathways on the way to or from foraging or
watering areas (Thotnas and West 1989). There is therefore an
inherent site bias that cannot provide unequd. vocal information on the
distribution of bats among sites or habitats using mist-nets as a
survey method (Thctnas and West 1989). Mist nets were used in this
study to document species occurrence, vrfiile realizing that there are
inherent biases in the method that select against the documentation
of some species.
A potential problem with capture methods such as mist-netting is mis-
identification of bat species. Most species in Montana can be
identified easily using one of several available dichotcmous keys,
such as Van Zyll de Jong (1985). When there was any question of
identification during this study, the bat in question was collected
and taken to an expert for positive identification. Bats most easily
24
cxjnfused on the Deer lodge National Forest are the Fringed bat (Myotis
thysanodes) with the Northern long-eared bat {Myotis evotls) , and the
Yuma bat (Myotis yunanensis) , California myotis {Myotis
calif omicus) , and Little brown bat {Myotis lucifugus) oorplex.
Ftelative density
Relative density between sites and between habitats by different bat
species can be determined using ultra-sonic bat detectors.
Discussions of the various types of ultrasonic detectors, along with
their inherent strengths and weaknesses, can be found elsevdiere (see
Fentcn 1988, and Thomas and West 1989). One or two tunable
heterodyne detectors were used during this study. These detectors
can be tioned to a number of frequencies, but can only scan a narrow
band at one time. Detectors were normally set at 40 kHz during
surveys, as most bats in Montana can be detected at that frequency.
If a bat was heard long enough, an attempt was made to determine its
lowest detectable frequency, as several species, or groups of
species, can be identified using this characteristic.
The intensity of the echolocation call differs between species, as
well as the frequency range of the call. This characteristic biases
relative density infomiation between species. Bats with intense
vocalizaticffis, such as Hoary bats {Lasiurus cinereus) or Big brown
bats {Eptesicus fuscus), are much more likely to be detected than
tlxDse with weaker vocalizations, such as Townsend's big-eared bat.
Myotis species fall between these extremes in intensity of their
25
vocalizations. In effect, the effective area sanpled by the detector
is much larger for the strong emitters than for the moderate or weak
emitters. Thus, direct oompariscns of relative density between
species based solely on bat detector results is unwise.
Though some effort was made to determine species heard with bat
detectors, the observers were not experierjoed enough to feel
confident in the accuracy of their identification. Considering this
and the inherent bias discussed above, no effort was made during this
study to determine relative density of bats between species, or of
species at specific sites.
Habitat use
To analyze the use of various habitats, and the inportanoe of various
components of these habitats within the Deer lodge National Forest,
bat use was determined from the results of surveys conducted with
ultrasonic bat detectors. Bat use was defined as "bat passes per
hour," as heard on a bat detector. An observer cannot generally
differentiate between one bat passing several times, and several bats
passing once, so the measurement is quite relative. No attertpt was
made to determine species; all bat echolocation calls detected were
recorded and used as a measure of relative density. Bat activity was
arbitrarily assigned to categories of high (more than 10 passes per
hour ) , moderate ( 5 to 9 passes per hour ) , and low ( less than 5 passes
per hour). This classification is completely arbitrary, and is based
on results that occurred across the Deerlodge National Forest during
26
1991. As noted in the Results secticn, of 30 hours of transects run
during 1991, only 10% recorded more than 21 bats per hour, and about
85% had less than 10 bats per hour. In other localities 10 or even 60
bat passes per hour may be ccMTsidered low activity, but these
categories will serve for the analysis of relative habitat use on the
Deerlodge.
Assuming that the degree of bat activity associated with a site
cxDrrelates with the preference by bats for some ccnpcxient of the
habitat of that site, analysis of bat activity by habitat component
should indicate which conponents bats appear to be selecting for, or
against. For instance, 60 percent of the sites surveyed in which
beaver ponds were a conponent of the habitat had high bat activity,
while another 20% had moderate activity (Table 2). Of sites with
mature Douglas fir, 33% had high activity and 17% moderate activity.
^Jo sites with lakes or clearcuts had high activity, but 100% of those
sites with clearcuts had moderate activity and 67% of the sites with
lakes had moderate activity. Conbining features, 63% of those sites
surveyed that had both nearby rock outcrops and riparian areas had
high or moderate activity, and 46% of the sites with riparian areas
and either Douglas fir or mature hardwoods had high or moderate
activity (Table 2).
The habitat oomponents at v^iich a third or more of the sites
featuring that component had high bat activity were: beaver ponds
(60%), rock outcrops (45%), mature hardwoods (38%), and mature
27
Douglas fir ( 33% ) . Features at vdiich a third or more of the sites
with that cxxnponent had moderate activity were: cleancuts (100%),
lakes (67%), and lodgepole pirie (36%) (Table 2).
Of those sites that had high bat activity, 100% of them had rock
outcrops nearby, 100% had riparian areas nearby, 100% of them had
riparian areas with either Douglas fir or mature hardwoods, or
riparian areas with rock outcrops nearby ( Table 3 ) . Components that
were part of the habitat at half or more of the sites with high bat
activity, in addition to those mentioned, were beaver pcxids (60%),
mature Douglas fir (80%), and mature hardwoods (66%). No sites with
high bat activity had caves or lakes nearby, though a third of the
sites with moderate activity had caves or lakes nearby ( Table 3 ) .
In a study of forest bats in Oregon and Washington, all species
except the Silver-haired bat (Lasionycterts noctivagans) in
Washington, were detected at dramatically higher rates in old-growth
stands than in young or mature stands of Douglas fir (Thomas and West
1991). Bats were between 2.5 and 9.8 times more abundant in old-
growth than in young or mature stands in both regions. Thomas and
West (1991) speculated that the activity of the Myotis species, the
Big brown bats, and the Silver-haired bats in Oregon were more
abundant in old-growth because that habitat provided an increased
variety and abundance of day roosts.
Perkins and Cross (1988) reported that all of the Hoary bats and most
28
of the Silver-haired bats in their stuc3y roosted in old-growth
Douglas fir. They speculate that Hoary bats prefer these older trees
because they roost in foliage, and older trees provide a combination
of shelter, open space to gain flight vrtien leaving the roost, and
ijimediate accessibility upon return. Silver-haired bats appear to
prefer older Douglas fir trees because the bark tends to pull away
from the bole providing crevices for shelter. Older trees are also
may provide roosting crevices or cavities created by wind and
lightning damage, shed limb holes, excavations by cavity nesting
birds, cracks in the wood, and so on (Perkins and Cross 1988). Old-
growth ponderosa pine provided some roosting sites, but was not
selected as often by bats as old-growth Douglas fir because bark
ridges are not as deep and bark exfoliation is not as common in
ponderosa pine ( Perkins and Cross 1988 ) .
Bats may roost in numerous sites within a forest exclusive of old-
growth timber. Old buildings, including recreational cabins and
buildings associated with abandoned mines, provide favored sites for
some species, inclioding the Little bixiwn bat and the Big bmwn bat
(Fenton 1992), but these are often unavailable in much of the
forested west. Caves and adits may provide roosting sites for many
species of bats ( Fenton 1992 ) . Many of the Myotis species including
the Fringed bat, the California myotis, and the Small-footed bat
(Myotls ciltolahnxa) , have been found roosting in fissures and under
rock slabs (Thomas and West 1986).
29
Thomas and West (1991) reported that, although old-growth stands of
timber had much greater bat activity than other forest stands, Myotis
species did not appear to forage there. In some cases, they
reported, feeding rates were dramatically greater over water. Though
insect density was similar in forested and lacustrine habitat, Lunde
and Harestad ( 1986 ) found bat activity 75 times greater in the
lacustrine habitat. They reported no bat activity in cutover forest
though insects were abundant in that habitat.
Cave and adit surveys
Seven caves and several abandoned mine adits on the Deerlodge
National Forest were searched for evidence of bat use during the
summer of 1991. No summer roosting sites were located in these caves
or adits. However, bats could be using any of these as autumn
swarming locations, or winter hibemacula, and this possibility
cannot be ruled out until all are surveyed at appropriate times (in
southwestern Montana, late Septonber to mid-October for elevations
above 5(XX) ' , 3 weeks later for lower elevations ) .
SUNWARY
Six species of bats, representing four genera, were documented by
capture during this phase of the study. These were the Big brown bat
(Eptesicus fuscus), the Little brown bat {Myotis lucilugfus) , the Yuma
bat {Myotis yumanensis), the Long-eared myotis {Myotis evotis), the
Hoary bat (I-asiurus clnereus), and the Silver-haired bat
( Lasionycteris roctivagans ) .
30
Relative bat densities varied between habitats. Those with rock-
outcrops, beaver ponds, mature hardwoods, mature Douglas fir, or
riparian areas nearby had the greatest bat activity.
Findley ( 1993 ) stated that an increase in species richness
aoccnpanies increased availability of roosts. "Forested regions
lacking cliffs, caverns, and caves support fewer species, and those
that do occur are known to use trees as daytime roosts in summer.
Mountainous, broken topography with opportunities for roosting in
crevices, cliff faces, caverns, and caves support richer communities"
(Findley 1993).
Management prescriptions that maintain undisturbed stands of old-
growth forest, especially old stands of Douglas fir and mature
hardwoods, the maintenance of healthy riparian areas, and the
preservation of caves and access to abandoned mine adits will provide
roosting and foraging habitat for a diversity and abundance of bats.
Management activities that promote large lodgepole pine stands, and
even-aged management will not.
31
LITERATURE CITED
Anthony, E.L.P. 1988. Age determination in bats. In Ecological and
behavioral methods for the study of bats. T.H. Kunz Ed.
Smithsonian Institution Press, Washington, D.C. 533 pp.
CamE±iell, N.P. 1978. Caves of Niontana. Bulletin 105, State of Montana
Bureau of Mines and Geology, Butte. 169 pp.
Fentcn, M.B. 1988. Detecting, recording, and analyzing
vocalizations of bats. In Ecological and behavioral methods for
the study of bats. T.H. Kunz Ed. Smithsonian Institution Press,
Washington, D.C. 533 pp.
Fenton, M.B. 1992. Bats. Facts on File. New York, NY. 207 pp.
Fenton, M.B. and G.P. Bell. 1981. Recognition of species of
insectivorous bats by their echolocation calls. J. Mammal.,
62:233-243.
Finch, D.M. 1992. Threatened, endangered, and vulnerable species of
terrestrial vertebrates in the Rocky Mountain Region. Gen.
tech. rpt. RM-215. USDA Forest Service, Rocky Mountain Forest
and Range Experiment Station, Fort Collins. 38 pp.
Findley, J.S. 1993. Bats: a ccmiunity perspective. Cambridge Univ.
Press, Cambridge.
Center, D.L. 1993. Animal species of special oonoem. Mcntana
Natural Heritage Program, Helena. 11 pp.
Hill, J.E. and J.D. Smith. 1984. Bats: a natural history. Univ.
Texas Press, Austin. 243 pp.
Hoffman, R.S. and D.L. Pattie. 1968. A guide to Montana mammals:
identification, habitat, distribution, and abundance. Univ.
Montana, Missoula.
Kunz, T.H. and A. Kurta. 1988. Capture methods and holding devices.
In Ecological and behavioral methods for the study of bats.
T.H. Kunz Ed. Smithsonian Institution Press, Washington, D.C.
533 pp.
Lunde, R.E. and A. S. Harestad. 1986. Activity of little brown bats
in coastal forests. Northwest Science 60:206-209.
Mumma, J. 1991. Updated Northern Region sensitive species list.
Unpubl. memo. Northern Region, USDA Forest Service, Missoula.
32
Raoey, P. A. 1988. Reproductive assessment in bats. In Eoolcgical
and behavioral methods for the study of bats. T.H. Kunz Ed.
Smithsonian Institution Press, Washingtcn, D.C. 533 pp.
Thomas, D.W. and R.K. LaVal. 1988. Survey and census methods. In
Ecological and behavioral methods for the study of bats. T.H.
Kunz Ed. Smithsonian Institution Press, Washingtc«i, D.C. 533
pp.
Thomas, D.W. and S.D. West. 1986. Forest age associations of bats
in the southern Washington Cascades and Oregon Coast Range.
Final rep. PNW-84-234. Forest Sciences Laboratory, Univ. Wash.,
Seattle.
Thomas, D.W. and S.D. West. 1989. Sampling methods for bats. Gen.
tech. rep. PNW-GTR-243. Pacific Northwest Res. Sta., USDA
Forest Service, Portland.
Thomas, D.W. and S.D. West. 1991. Forest age associations of bats
in the southern Washington Cascade and Oregon Coast ranges. In
Wildlife and vegetation of unmanaged Douglas-fir forests.
Pacific ^forthwest Res. Sta., USDA Forest Service, Portland.
Thcnpson, L.S. 1982. Distribution of Montana an^dxLbians, reptiles,
and mammals. MT Audubon Council, Helena.
Tuttle, M.D. 1974. An ijiproved trap for bats. J. Mammal ., 55 : 475-
477.
van Zyll de Jong, CO. 1985. Handbook of Canadian mammals : bats .
National Museum of Canada, Ottawa. 212 pp.
Worthington, D.J. and H.N. Ross. 1990. AbundaiK)e and distribution
of bats in the Pryor Mountains of south central Montana. MT
Natural Heritage Program, Helena.
33
APPEMDIX I
BAT SURVEY FIEXD FORM
MTNHP 92/2-1
DATE:
LOCATION:
WEATHER:
TEMPERATURE
l-TIND
CLOUD COVER
HUMIDITY
LEGAL DESCRIPTION:
(start/time) (finish/time)
SITE CHARACTERISTICS:
\'ECETA'nON (tree and shrub fpripK, carop/ co^rags, size, desty, dBstrikudaQ) ■
Water (s&«ini \»i±h, depth, sp3ed, bonk co.'er, pcnd cr lake cae, erxi^rt \«^t2txrO •
LOCALCEOLOGY (jtxitype,aicrtrfcuttTDpsardife)-
CAVK OR ,\DnS (in >.xinil>'?, sLtSus Eur%«>«I?)
Note: if bat sur^ is .it a spodfic ct^« or adit, describe Yere ani oocnplete a C3^« inxoitny fcnn)
MIST NET (OR TLTTTLE TR^P) RESULTS:
Number and sbes rfnust rets set 18* 20 4Z 03 «}»■ ( )
VtfMhAien set (trail, stremii, ozopf, pond, nvodow, cave atiaiut, etc - nxnd runJber and actting):
TUllB trap uwT Y / N V\"Im« sot
34
APPENDIX I (cont.). Nms'HP92M
Bats captumi Y / N (Speoos soi and ranrte-):
For ench bat caftumj. recciTd:
SPECIMEN NUMBER; DATE; LOCATION:
TTMErfCAPTUPLE; Courty, MT
D!
aSoc M F Un 3)AsE M Juv Un
4) Reprod £i.Tts P: Lic/KonLx, Crav / Pcsipx-am. Unin Kcne; M; Scrotal / Ncnaaa
5) We^ . pains. Fcreonn len^ mm. CXher c^a-'r tharadenaxx
6) CaiuiM to Cnat t>-pe and ha^i, caiieiai cfbet and nmkiii^fean, cnDBClBd cr jdaased):
Fcr eoch bnt captred, recxd
SPECIMEN NUMBEP>; DATE;
TIMEd"CAPTUE£: Ccua^, MT
U Specks
2jSoc M F Un 3)A^ Ai Jiw Un
4) Reprod ttaajE F: Lac/NonLac, Crav / Po6{partun\ Unkn None; M: Sortal/Norscict
5) Wa^Ti; . paiiB. Foreor.n lenghl; mm. Other spedSc chaiactnisbcs:
6) Calul1alts(nat^7xnJ1dhei^oartlacnoffa^tanlma^kmelikaIS,oclbaalc^Idee^e^
35